-ANDROID := /opt/android-sdk-update-manager/platforms/android-10/android.jar
-PACKAGE := org.pileus.spades
-OUTPUT := bin/Spades.apk
+ANDROID ?= /opt/android-sdk-update-manager/platforms/android-10/android.jar
+PACKAGE ?= org.pileus.spades
+OUTPUT ?= bin/Spades.apk